I'm always surprised by how many partnership returns are floating around out there, especially for new businesses that can't use the excuse of "that's how it has always been done."  If she wanted to be a limited partner, why didn't they do an LP or LLC?  Preferably taxed as an S corp.  If she didn't participate last year in decision making, that means her decision was to go along with what her siblings decided.  This year, she still has 25% of the vote, right?  And for all we know, the partnership agreement requires unanimity.  

Maybe there's a way to get out of paying SE tax, that others can provide here.  You have my sympathy, for coming in on this after the fact, rather than being asked about the tax consequences before she made such an important decision.